A monolithic multilayer capacitor includes a body portion, referred to herein as a "chip," and also includes a pair of end terminations. Such a capacitor has a stacked configuration having alternating conductive and dielectric layers, with the conductive layers defining first and second sets. These layers are contained in the chip. In the capacitor, all the conductive layers in the first set are electrically connected together at one end of the chip by one of the pair of end terminations; all the conductive layers in the second set are electrically connected together at the opposite end of the chip by the other of the pair of end terminations.
Various types of materials can be used to make a monolithic multilayer capacitor. When ceramic is used as the dielectric, the capacitor is referred to as a monolithic multilayer ceramic (MLC) capacitor. In a monolithic MLC capacitor, a platinum/palladium alloy is commonly used for the conductive layers. In other multilayer ceramic capacitors, any of various materials, including silver, gold, and platinum, is used for the conductive layers. In any case, the capacitor is functional only if at each of the opposite ends of the chip the respective end termination provides a good electrical connection to the edges of the conductive layers in the chip, such that all the conductive layers in one set cooperate as one electrode and all the conductive layers in the other set cooperate as another electrode.
One prior art approach that has been used to electrically connect such conductive layers together involves a liquid coating process. A representative example of this liquid coating process can be more particularly described in the concrete context of the manufacture of MLC capacitors. In this context, the prior art liquid coating process entails preparing an ink comprising silver and a glass frit for use as a coating material. In sequence, one end of the MLC chip is dipped into the ink, and later the opposite end is dipped into the ink. After dipping, the chip is placed in an oven and subjected to a firing cycle where the glass frit bonds to the ceramic and the silver in the ink mixture provides the electrical continuity and electrical termination joining the conductive layers within the chip and thus provides the end terminations for the resulting functional capacitor. A capacitor prepared in this manner can be used as a surface-mounted device; that is, the capacitor can be bonded to a printed circuit board by directly reflow soldering or by using conductive epoxy that electrically connects plated conductors on the board directly to the end terminations of the capacitor. Alternatively, a separate lead can be attached to the film at each end of the capacitor to provide a pair of leads for inserting into plated holes in a circuit board or for otherwise connecting the capacitor to the other electrical circuitry with which it is to be used.
In addition to the above-described process, the prior art includes U.S. Pat. No. 3,992,761. This patent discloses an approach to the problem in a production operation of providing an individual termination at each end of many multilayer capacitor chips. The disclosed approach is to mount the capacitor bodies in a support sheet and encapsulate the support sheet and the capacitor bodies in a plastic block with the ends of the capacitor body being exposed at opposed surfaces of the block. According to the disclosed approach, the exposed ends of the capacitor bodies are simultaneously plated via an electroless plating process with a termination film and then with a solder film and the terminated capacitor bodies are thereafter removed from the block.
In prior art surface-mounted capacitors, the end terminations not only cover the end of the chip but also forms a thin, surface contact adjacent the end, and often a complete band around the end of the chip. This was typically done for two reasons. First, during surface mounting of the capacitor, the solder will "float" the capacitor slightly above the board, thereby providing clearance beneath the bottom surface of the capacitor and allowing use of cleaning fluids to remove residual flux. Second, the capacitor can be made symmetrical so that it does not have to be specially oriented during the assembly operation preceding the soldering operation.